Various types of sensors to determine the composition of exhaust gases from internal combustion engines have been proposed. One such sensor, for example, is described in U.S. Pat. No. 4,019,974, Weyl and Steinke, issued Apr. 26, 1977. This sensor has a solid electrolyte body which is made in form of a closed tube and in which electrodes and conductive tracks are formed. It is comparatively expensive to make such a sensor and to apply the respective electrodes, conductive tracks, and other layers thereon, as well as to make the electrical connections. The tubular element must be fitted into a longitudinal bore of a metal housing. The structure requires a comparatively large amount of materials and is labor-intensive. The response sensitivity and speed of such a sensor can still be improved. This type of sensor operates according to the potentiometric principle, that is, it functions as a true voltage-generating cell, providing an output potential when the exhaust gases and the reference gas have certain oxygen content relationships.
It is desirable to provide a sensor structure which can operate in accordance with the potentiometric principle but which, also, lends itself to use as a polarographic sensor, if suitably formed. A polarographic sensor is described, for example, in U.S. application Ser. No. 6,093, filed Jan. 24, 1979, Dietz, to which German Published Patent Disclosure Document DE-OS No. 27 11 880 corresponds. This sensor also is difficult to construct and it would be desirable to improve the sensor construction so that the sensor structure can be made at a lesser cost and with a higher degree of reproducibility, while providing a sensor having better response characteristics.